使用ESBT设计逆变电焊机的辅助电源

Design of 3 phase auxiliary power supply for inverter welding machine based on ESBT

设计了一个基于射极开关双极型晶体管ESBT和UC3845的电焊机三相辅助电源。详细说明了基于高压大电流三极管和低压大电流MOSFET管串联形成的新器件ESBT的工作原理;内部MOSFET直接用PWM驱动,内部晶体管用比例基极驱动电路驱动,比例基极驱动电路电流变压器的磁心选取原理和变压器一、二次绕组的设计流程,并给出了相关周边元件参数的选择公式。同时分析了380V输入和6路输出的反激式电焊机三相辅助电源的设计过程,并探讨了在输出轻负载时次谐波振荡的形成原因以及相关的波形。通过PWM的振荡波形由外部所加的电容引入斜坡补偿,可以有效地抑止电源在高输入电压轻载或空载时产生的次谐波振荡,并给出了加入斜坡补偿后反馈脚的对比波形。

A three phase auxiliary power supply for inverter welding machine based on Emitter Switched Bipolar Transislors（ESBT） and UC3845 is designed in this paper.ESBT in which bipolar transistor is in series with MOSFET features with high voltage,low conduction loss and high operation frequency.The operation principle of ESBT is also presented.MOSFET inside ESBT is driven by PWM controller and bipolar transistor is driven by external proportional circuit.The method of selecting magnetic core and primary and secondary windings and the values of other parts in proportional driving eircuit are diseussed.The design of auxiliary power supply of welding machine with 6 outputs is given.The cause of sub-harmonic oscillalion at high input voltage and light load is analyzed.The slope compensation circuit via a capacity is added to resist sub-harmonic oscillation.Some waveforms are shown in the end.